Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$123.41	11.783%	$137.9514	$137.95	$137.95	$138.00
Purchase #2	$100.31	4.798%	$105.1229	$105.12	$105.10	$105.10
Purchase #3	$13.39	10.412%	$14.7842	$14.78	$14.80	$14.80
Purchase #4	$37.67	3.398%	$38.95	$38.95	$38.95	$39.00
Purchase #5	$105.43	13.142%	$119.2856	$119.29	$119.30	$119.30
Purchase #6	$68.27	4.699%	$71.478	$71.48	$71.50	$71.50
Purchase #7	$221.77	10.387%	$244.8052	$244.81	$244.80	$244.80
7 purchase totals =	$670.25		$732.3773	$732.38	$732.40	$732.50